In conventional semiconductor fabrication processes, there are number of techniques for warming the wafers back to room temperature after low temperature implantation is complete. In one such technique, the wafer is warmed directly by the platen. In another, room temperature air is injected into the load lock and used to warm the wafers slowly. Lastly, a single tube-type lamp may be positioned inside the load lock to warm the wafers.
However, all these conventional techniques have disadvantages. Heating the platen directly results in low wafer per hour (“WPH”) and reduces the throughput as it takes more time of the processing chamber. Injecting room temperature air into the load lock also results in low WPH and wafer spotting defects due to water condensation resulting from mist, in addition to absorbing a lot of time and negatively affecting throughput. Those techniques utilizing a single lamp to warm the wafers results in non-uniform heating, which further causes non-uniform dopant diffusion and non-uniform device behavior from wafer to wafer and from die to die.
Accordingly, there is a need in the art for a wafer warming technique which alleviates or eliminates these disadvantages.